This invention relates to sewing machine embroidery or pattern stitching, and more particularly, to arrangements in a sewing machine for automatically performing predetermined group stitch patterns.
It is known primarily in the industrial sewing machine art to provide for the sewing of group stitch patterns such as buttonholes, monograms, and the like by means of a fabric shifting clamp with clamp shifting actuator and pattern means devoted exclusively thereto. In the household sewing machine art, group stitch attachments are well known driven by reciprocation of the needle bar or by motion of a work feed actuator and influenced by self contained patterning means, as for instance, by a pattern cam or the like associated with the attachment.
With the advent of electronic control of stitch pattern formation in sewing machines and the increases in complexity and data storage capacity of electronic memories and data processors as compared with prior art mechanical patterning means such as cams and the like, prospects seem favorable for the execution of group stitch patterns of correspondingly increased complexity by the use of such electronic memories.
While it might be possible to utilize pattern data extracted from an electronic memory for influencing the work shifting frame of a group stitch attachment to a household sewing machine by supplying actuators in the attachment which are responsive to the data extracted from the electronic memory and which are committed specially to driving the work shifting frame, the limited space which is available in such attachments, the excessive costs involved in providing such specially committed actuators, and the necessity to provide electrical connection between the sewing machine and such an attachment all militate against such an approach as a matter of commercial practicability.
It has been proposed to drive a work shifting frame of a group stitching device by harnessing the work transporting capabilities of the sewing machine stitch forming instrumentalities under control of electronic stitch patterning means. In other words, by feeding the work fabric in one direction with the sewing machine feed dog and in another direction by using the sewing machine needle as a work feeding means, the work fabric itself serving as a link in the drive of the work holding frame. There are drawbacks, however, to this proposal; one disadvantage being the undersirability of utilizing the work fabric as a drive link because of uncertainty as to the characteristics of work fabrics for this driving function particularly when the choice of fabrics may be completely out of control of the mechanism designer. Another disadvantage of such a proposal is that to whatever degree the stitch forming instrumentalities are so harnessed to move the work holding frame, the effectiveness of that stitch forming instrumentality simultaneously to produce conventional zig zag stitch patterns is diminished.